This is article discusses changes that occur in our bodies as we age, what researchers believe causes aging, and things that we can do to feel healthier (and live longer).

The human body is a complex organism, with literally millions of delicately balanced and complex chemical reactions that sustain life and growth. Much of the growth and renewal in our bodies comes from the genetic code stamped into each of our cells, as well as our individual metabolism.

These differences can determine how long we live and how well we age, our predisposition to certain diseases as we grow older, and how well we heal, to name a few factors. In this article, we will be looking at how we age, and some of the normal and abnormal changes that can occur.

Normal Changes That Occur As We Age
As we age, there are changes that will occur as the decades pass. Scientists are still studying these changes and exactly why they occur. Some of these changes include:

Memory and Cognition:
By the age of 50 or 60, small changes in overall intellectual functioning begin to be noticed. These are usually covered by a still intact verbal ability, and are usually not intrusive. But by age 75, in some individuals cognitive loss can be much greater, and may not be covered for as well.

Normally, verbal skills will remain untouched until we reach our eighth decade when they also begin to decline, although this is individual and varies greatly from person to person. People tend to rely more on “crystallized” intellectual functions (abilities “burned into” our memories by repetition that were learned earlier in life) as they age. But intellectual functions that involve complex abilities such as abstract reasoning or solving difficult problems is less efficient as the decades pass, in part because as we grow older, the speed that neurons transmit information slows down. This means that processing the information becomes less efficient over time.

Reaction times also slow, making driving more difficult. Long term memory stays with us though, and is more easily accessed than short term memory as we age.

Skeletal/Muscle:
Our strength and muscle mass peaks between the ages of 20 and 30, and then begins a gradual decline. This process can be accelerated by an inactive lifestyle. The small hand muscles also waste, and numbness can occur in the toes and fingers in elderly people. Arthritis can occur which makes bending, turning, or standing up more difficult.

Our brain mediated sense of balance remains, however, throughout the life span if illness is not present.

By age 40, the waist size begins to increase as muscle converts into fat which becomes centralized around the torso, while muscle wasting occurs in the legs and arms. And by age 60, the height begins to shrink as gravity causes vertebral compression..

Cardiovascular/pulmonary/GI
There is a gradual decline in the lung capacity and cardiac capacity as we age after the age of 30 to one half of their capacity by age 60. The cardiac stroke volume and rate go down as the years continue. This process is more rapid in individuals who are sedentary.

The emptying of the stomach is delayed in the elderly person, and the muscles in the intestines that move food through it for digestion also slow down as we age. Albumin (blood protein) levels drop as we become older.

The kidneys and liver functions begin to decrease, and medications cannot be cleared as easily in the older person, making a toxic reaction or side effects more common. The percent of our bodies made up of water decreases as we age.

Skin/hair
Our skin begins to wrinkle in response to a loss of the subcutaneous fat layer, and the weakening of the underlying collagen structure. Hair becomes thinner and begins to gray as well.

Vision and Hearing
By about age forty, our eyes begin to lose the ability to accommodate, or to reshape the lens to focus on nearby objects. This is in part due to the fact that the lens, which is normally clear and flexible at birth, begins to harden and grow yellow over time. This loss of flexibility can contribute to presbyopia, or the need for reading glasses during middle age.

We also begin to lose the ability to look upwards as we age. By age 30, hearing begins to be affected, and the ability to distinguish sounds can diminish as time goes on.
Smell/taste
There is a gradual loss in the sense of smell and taste over time, with difficulty in distinguishing nuances.

Pathological (Illness Related) Changes
At the turn of the century, most deaths were caused by infectious diseases: tuberculosis and pneumonia together were responsible for one fifth of all deaths. Infant mortality was also higher in 1900, when one out of four infants would not live to the age of 5. In the past decade, 99% of all children born in the U.S. lived to enter kindergarten, and 53 % of deaths occuredr in people age 75 or older. And now, at the start of the new millennium, two thirds of the deaths in the United States are caused by three diseases often associated with aging: heart disease, stroke, and cancer.

Heart Disease and Stroke
Heart disease and stroke are both manifestations of cardiovascular disease. The causes of this disease that creates clogging of the interior of arteries with plaque, or fatty and calcified material are complex. Diet and cholesterol levels, insulin resistance, free radicals, sedentary lifestyle, and changing hormone levels as we age have all been discussed as possible causes by researchers. Current research is looking into methods of preventing or delaying the onset of these diseases, as well as the early recognition and improved treatment of those affected.

Cancer
Research has unraveled some clues as to why certain cells in the body begin to proliferate and cause what is called cancer. We now know that genetics may play a role, and that as we age, our ability to both fight off these cancerous cells, as well as damage from a lifetime of exposure to substances such as free radicals and other toxins may all play a part in its genesis. Most importantly, scientists are using this increased knowledge to develop new medications and treatments that target the immune system, or that target cancer cells specifically while leaving normal cells alone.

Alzheimer’s Disease
Scientists are now beginning to find out some of the mechanisms that underlie Alzheimer’s disease. Nerve cells slowed or affected by clumps of beta amyloid plaques and tangles of tau proteins start to lose their function.

Another protein that is involved in moving cholesterol, ApoE, may also be involved in the development of beta amyloid plaques.

Current research in the battle against Alzheimer’s is directed at substances that can overcome the effects of both tau proteins and ApoE formation. A possible vaccine that may stop the formation of plaques and tangles, and inhibitors that fight against the formation of beta amyloid plaques are also being developed.

More controversial research is looking at stem cells (embryonic cells that later differentiate into organ cells) as one treatment. These embryonic precursor cells may have the ability to turn into neural tissue and could help regenerate damaged neural tissue.